Experimental evidence for the microscopic mechanism of the unusual spin-induced electric polarization in GdMn2O5

Abstract

We report in this paper the temperature evolution of the magnetic structure of GdMn2O5, in the range 2 K to 40 K, studied by neutron diffraction on an isotope enriched powder. We detail a thorough analysis of the the microscopic mechanisms needed to release the different magnetic frustrations that are at the origin of the polarization. In addition to the usual exchange-striction term, known to be at the origin of the polarization in this family, an additional exchange-striction effect between the Gd 3+ and Mn 3+ spins is found to be responsible for the very large polarization in the Gd compound.

Weak exchange striction between the 4f and 3d ions in the multiferroic GdMn2O5Sheng1, Tong2, Ye3 et al. 2019Phys. Rev. B3000View full textAdd to dashboardCite

“…The corresponding charge valences of the Mn 3+ 1 and Mn 3+ 2 spins are +3.12(2) and +3.00(2) as calculated using the bond valence summation method 27 . Figure 2 illustrates the spin structure at 5 K. The configuration is almost identical to the result by Lee et al 9,25 , but bears subtle difference with the recent neutron powder diffraction report 21 . The Gd 3+ and Mn 3+ spins marked in Figure 2 have FM coupling, instead of AFM correlation described in Ref.…”

“…The Gd 3+ and Mn 3+ spins marked in Figure 2 have FM coupling, instead of AFM correlation described in Ref. [21]. The latter configuration is simply the nontrivial magnetic domain with the 2 1 -rotation axis applied instead of the mirror plane across (1/4, 0, 0) in our case.…”

Pressure-induced commensurate order in TbMn2O5 and DyMn2O5 : Influen

“…It seems that either one or the other mechanism may dominate, depending on the compound or temperature range considered [1,[3][4][5][6][7][8]. The relative roles of such mechanisms in the low-temperature spin order ferroelectricity are actively investigated in the series [9][10][11][12].…”

Pressure-dependent X-ray diffraction of the multiferroics RMn2O5

“…The different exchange interactions. perpendicular (the J 3 term does not cancel), it is the release of the magnetic frustration over J 3 that is responsible for the onset of polarization (Blake et al, 2005;Yahia et al, 2018). The difference between J AFM 3 and J FM 3 , which is a consequence of the exchange-striction mechanism, is thus directly connected to the electric polarization.…”

“…Instead an 'exchange-striction' mechanism, first proposed by Chapon et al (2006), was recently established (Yahia et al, 2017). In addition, the microscopic mechanism of the atomic displacements responsible for the polarization was unveiled (Yahia et al, 2018).…”